The research program features the integrated application of techniques in biochemistry, physiology, and light and electron microscopy in a series of specific experiments on blood platelets, red blood cells, the blood vessel wall, and the lung; and includes basic work on cells, membranes, and the microvascular system in animals and applied work in man. The microvascular system and the formed elements in the blood are being studied by light, electron and quantitative vital microscopy in animals and, where applicable, in man. In man the study will include blood vessels in lung, kidney, myocardium, brain and extremities. In our basic work on the formed elements attention is focused on the requirements of platelets for aggregation, the release reaction and phagocytosis, and means of inhibiting or controlling these processes. The platelet membrane will be modified biochemically in a quantitative manner, its surface characteristics determined after each modification, and these findings correlated with the functional capacity of the platelet and changes in its ultrastructure. Attention is also being given to further in vivo quantification of variables at the microvascular level.